1. Field of the Invention
The present invention relates to a blood components collector unit which is useful for separately collecting blood components, particularly for separately collecting plasma and blood cell-enriched blood from the blood of a healthy human.
2. Discussion of the Prior Art
In recent years, there has been an increase in demand for transfusions of blood components. Conventionally, several methods have been proposed for separately obtaining blood components. One of the methods, which was first proposed, was the so-called centrifugal separation method in which whole blood is taken from a donor and then the blood is subjected to centrifugation, causing the blood to separate into plasma and blood cell components.
On the other hand, there is a demand for only the plasma component of blood. For meeting the demand, there have been proposed methods for collecting only plasma from whole blood, for example, (a) the so-called extracorporeal circulation method in which a membrane type plasma separator is directly connected to a vein of a donor through pumping means, and whole blood is withdrawn from the donor with aid of the pumping means and conveyed to the membrane type plasma separator in which the blood is separated into plasma and blood cell-enriched blood, and the separated plasma is then collected while the blood cell-enriched blood is returned into the donor, and (b) the so-called dropping method in which whole blood is withdrawn out of the donor utilizing the force of gravity and conveyed to a membrane type plasma separator in which the blood is separated into plasma and blood cell-enriched blood, and the separated plasma is then collected while the blood cell-enriched blood is returned into the donor utilizing the force of gravity in the same manner as in installation.
However, the above-mentioned centrifugal separation method has a disadvantage in that a centrifugal separator which is an elaborate apparatus needs to be used. Further, in this method, since the respective blood components are unstably separated into two layers due to the difference in specific gravity and separately collected by manual operation, the method is not only disadvantageous from viewpoints of ease in operation, cost and simplicity, but also has a high possibility that the collected plasma disadvantageously contains platelets and leukocytes, leading to an instability in quality of the collected plasma.
Further, in practicing either the extracorporeal circulation method or the dropping method, the donor and the plasma separator are kept connected directly to each other during the plasma separating operation and, hence, the rate of blood flow through the plasma separator must be set so as not to burden the body of the donor. Therefore, it is difficult to set the supply rate of the blood to the capacity of the plasma separator, so that the capacity of the plasma separator cannot be fully exercised. Moreover, any of the above-mentioned methods is practiced so as to collect plasma in an amount as much as 400 to 600 ml and, therefore, it takes a considerably long time for completion of the plasma collecting operation. Hence, the donor must be restrained for a long time until completion of the operation.
Further, in any of the above-mentioned methods, during the operation it is necessary to introduce an anticoagulant to the blood at a predetermined flow rate and, hence, even the dropping method, which is advantageous in that the method can be practiced using a simple apparatus, disadvantageously needs to involve the additional use of equipment for introducing an anticoagulant to the blood taken from the donor.
Moreover, in practicing any of the above-mentioned methods, the donor and the plasma separator need to be connected to each other throughout the plasma separation operation and, therefore, it is disadvantageously necessary to involve the additional use of means for safety such as a bubble detector and the like. Furthermore, in any of both methods, the blood cell-enriched blood is returned to the donor and, hence, there is a disadvantage in that the anticoagulant unavoidably enters the body of the donor together with the returned blood.
The so-called dropping method and an apparatus for collecting plasma to be used for the method are disclosed for the first time in European Patent Application Publication No. 0114698. In this publication, it is described that the conventional extracorporeal circulation method employing a membrane type plasma separator has disadvantages in that it is necessary to use various equipments such as a pump and a safety monitor, and that it is much more costly than that of the centrifugal method. The object of the invention of the above European Patent Application is to realize collection of plasma from the donor, while enjoying a high separation performance of a membrane type plasma separator, at a cost as low as possible and using an apparatus as simple as possible. The dropping method described in the above European Patent Application Publication No. 0114698 is far simpler in operation than the other conventional techniques for collecting blood components separately and the apparatus used in the dropping method also is simple as compared with those used in the other conventional techniques.
The dropping method is excellent in its principle. However, as described hereinbefore, the plasma separation system disclosed in the European Patent Application Publication No. 01146980 has the following various disadvantages: (1) additional means are needed for introducing an anticoagulant to the blood taken from the donor, (2) since the rate of withdrawal of whole blood from the donor is preferentially set, the rate of plasma separation is necessarily limited according to the flow rate of whole blood, and (3) there is disclosed no measures for recovering valuable human blood which, after completion of the operation of separating blood components, inevitably remains in the circuit of the apparatus, particularly in the membrane filter plasma separator.
Moreover, the apparatus of the above European Patent Application Publication No. 0114698 has a major disadvantage in that it requires cumbersome various preparatory operations before the blood components collecting operation. That is, (1) various components of the apparatus such as the filtration unit and reservoirs need to be provided separately and must be rinsed before use with an electrolyte solution containing an anticoagulant, (2) the anticoagulant contained in the plasma collection bag and the blood cell collection bag needs to be thrown out before use, and (3) the components of the apparatus need to be assembled just before use. Moreover, during the operation, the apparatus is not closed at the inlet for introducing an anticoagulant from outside and, hence, it is possible that the separated blood plasma and blood cell components are contaminated with various germs.